Answer: Fraction of twins =
Fractions of triplets =
Fractions of quadruplets = 
Step-by-step explanation:
Since we have given that
Number of set of twins = 5
Number of sets of triplets = 2
Number of sets of quadruplets = 1
Total number of sets is given by

Now, we need to find the fraction of those students.
So, Fraction of twins is given by

Fractions of triplets is given by

Fractions of quadruplets is given by

The answer is a, all rhombuses have equal sides, if they have equal sides then day have equal angles.
Answer:
1. distance = sqrt( (7-7)^2+(2- -8)^2) = 10
2. check out desk (0,0 ) => distance = sqrt( (0- -9)^2+(0-0)^2) = 9
3. last corner ( -3, 4)
4. area = sqrt( (-10- -10)^2+(10-4)^2) x sqrt( (-3- -10)^2+(10-10)^2) = 6x7 =42
5. check desk (0,0), south direction = negative y axis => P_beginning (0,-20), P_end (0,-(20+25)) = (0,-45)
6. A(-2,-1) and B(4,-1) lie in y =-1. AB = sqrt( (-2- 4)^2+(-1- -1)^2) =6
=> area = 3.6x6 =21.6
=> peri = 2x(3.6+6) = 19.2
7. A(-5,4) and B(2,4), AB = sqrt( (-5- 2)^2+(4- -4)^2) = 7 => AB is base
=> p = peri = 7+ 8.3x2 = 23.6
=> area = sqrt[px(p-7)x(p-8.3)x(p-8.3)]
=sqrt[23.6x(23.6-7)x(23.6-8.3)x(23.6-8.3)] = 302.8
12000 = 2x - 1500
12000 + 1500 = 2x
13500 = 2x
13500/2 = x
6750 = x <=== original price